1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a storage medium readable by computer. More particularly, the present invention relates to an image processing apparatus, an image processing method, and a storage medium readable by computer, which are enabled to extract change information concerning an additional writing, such as a memorandum, made on a document including a text and image data, for example, a printed-out document, and also enabled to analyze a part of the document, which part may be tampered by the change information, and also enabled to issue a warning.
2. Description of the Related Art
In the field of image processing, various studies and developments have been made on the processes of extracting additional writing information on a memorandum written by a user into a document outputted from, for example, a printer or a FAX and of verifying whether the security document is tampered. Generally, in the processes of extracting the additional writing information and verifying the tampering of the document, an operation of comparing original document data with data representing an output document on which an additional writing or the like may be performed.
For example, JP-A-10-255027 discloses an apparatus configured to retain data representing an original document and a new manuscript document as data representing electronic documents and to extract the difference between these electronic documents to thereby extract additional writing information.
Further, JP-A-2003-264685 discloses an apparatus and method configured to detect change information in a case where additional writing and alteration are performed, and to judge whether the change information is tampered information. Furthermore, JP-A-2001-283231 discloses an apparatus configured to set an additional-writing inhibiting area set on paper and also configured not to take in additional writing information onto the additional-writing inhibiting area as image information, thereby preventing the apparatus from taking in unnecessary data and from performing unnecessary data-updating.
However, additional writings added to a document include writings made to tamper the document, in addition to ordinary writings such as a mere memorandum or comment. Conventional additional writing detection systems including the related art are configured to extract additional writing information and not to analyze whether the extracted additional writing information aims at tampering with a document.